The present invention is directed to a coal pipe monitor.
In particular, the invention is directed to method and apparatus for monitoring the flow of coal in a coal delivery system commonly employed in power plants. In such a system, the coal is delivered from a bunker through a conduit or downspout to a coal feeder. The coal is deposited on the feeder belt which transports the coal to a feed pipe. The coal flows through the feed pipe to a coal pulverizer. The feeder controls the rate of flow of coal to the pulverizer.
The pulverizer grinds the coal to a fine powder which is swept into a furnace by a primary air fan. This results in positive pressure of the hot primary air in the pulverizer. To maintain air flow from the feeder to the pulverizer, ambient temperature air is introduced into the feeder at higher pressure. This is referred to as seal air. The seal air serves to isolate the hot, coal dust laden air in the pulverizer from the feeder and the bunker.
The column of coal in the conduit acts as a restriction for the seal air. If the conduit should empty, the seal air would vent to atmosphere through the bunker. At the same time, the flow of coal to the pulverizer would stop, and the hot dusty air in the pulverizer would vent through the feeder into the bunker. The temperature in the pulverizer would rise, and the air/fuel ratio in the pulverizer would become lean and explosive. In addition, the furnace flame would become unstable, producing a situation with a very high potential for explosion.
The coal feeder is normally equipped to provide an alarm signal when the flow of coal into the pulverizer stops. At this time, however, it is too late to prevent the foregoing hazardous conditions in the pulverizer.
The present invention monitors the flow of coal through a zone of the conduit and senses an impending empty condition before the foregoing hazardous conditions occur.
The invention also provides data in respect to various operating conditions frequently encountered in the coal delivery system to permit rapid diagnosis of the system operation.